ST. LOUIS (AP) -- Clay Buchholz knows the difference between slight discomfort and pain.
He left a start against the Los Angeles Angels on June 8 in the middle of a seventh-inning at-bat after Erick Aybar fouled off a curveball. Buchholz got the win, improving to 9-0, but didn't pitch for the Boston Red Sox again until Sept. 10.
Against the Detroit Tigers last weekend in the AL championship series, his shoulder didn't feel quite right.
''Just had a little tightness, regardless of what it was, fatigue, whatever,'' he said Saturday. ''The last time I got hurt, I threw one pitch, and it's like, OK. I don't think I should throw another pitch. This time I went three-plus innings with tightness.''
Buchholz allowed two runs in five innings in Game 6 versus the Tigers, leaving with a 1-0 lead. The Red Sox fell behind before winning 5-2, and Buchholz's World Series start was pushed back a day to Game 4 on Sunday night, when Lance Lynn starts for St. Louis.
Buchholz doesn't have a decision to go along with a 5.40 ERA in three postseason outings.
''We go into tomorrow thinking that he's going to give us what he's been in the postseason,'' Red Sox manager John Farrell said. ''That might be a little bit shorter of an outing than maybe we've seen back in April and May, but he's also been very effective. And we're fully anticipating that to be the case tomorrow.''
Buchholz has averaged 90 pitches in three postseason starts. He was worried enough about his latest injury during the summer that he went to noted orthopedist Dr. James Andrews for an examination in late July
He threw off a mound before Game 3 at Busch Stadium on Saturday and said felt a bit rusty.
''I don't think there is any risk there,'' he said. ''My one thing that I have is to go and compete, go out there for as long as John wants to leave me out there, and give the team a chance to win to the best of my ability. Obviously, given the couple of days that I've been out so far, not a hundred percent. But I've said it a couple of times this year, I don't think anybody, especially at this time of the season, is a hundred percent.''
A 29-year-old right-hander, Buchholz was 12-1 with a 1.74 ERA in his abbreviated season, pitching just 108 1-3 innings. In June 2012, he went on the DL with esophagitis, which led to the erosion of his esophagus and gastrointestinal bleeding. At the time there was speculation anti-inflammatory medications were a factor.
''That was a pretty scary moment for me,'' he said. ''So I stayed away from the stuff that - the really strong anti-inflammatories. Basically been on the same stuff since the first time during the season, whenever I went on the disabled list. But I feel like I responded well to it. I've gotten more treatment in the past week than I did in the first week of being on the disabled list the first time.''